Fluid operated switch assembly



July 27, 1948. BE N 2,445,756

FLUID OPERATED SWITCH ASSEMBLY Filed June 21, 1944 3 Sheets-Sheet 1 asFrankfioberl Bea/7 INVENTOR.

BY w M. 4 477012 Y.

y 27, 1948. F. R. BEAN 2,445,756

FLUID OPERATED SWITCH ASSEMBLY Filed June 21, 1944 :s Sheets-Sheet 3Frank Robe/f 5am IN VENTOR.

w #5 BY )J ATTORN Patented July 27, 1948 FLUID OPERATED SWITCH ASSEMBLYFrank Robert Bean, Rochester, N. Y., assignor to F. A. SmithManufacturing Company, Rochester, N. Y.

Application June 21, 1944, Serial No. 541,349

17 Claims. 1

The present invention relates to a fluid operated switch assembly andmore particularly to a fluid operated switch assembly having one or moreadjustments to control switch operatin pressures.

Most fluid operated devices are responsive either to an increase or adecrease of fluid pressure or to a fluid pressure of predeterminedvalue. However, there is a'diflference between the pressure at which adevice is operated in one direction during an increasing fluid pressureand the pressure at which the same device is operated in an oppositedirection during a decreasing fluid pressure. Such pressure differentialis quite considerable in fluid operated switch assemblies wherein thepressure responsive member is arranged for substantial movement at apredetermined fluid pressure and so as to produce critical operationand/or rapid opening or closing of the switch assembly.

In many circumstances it is quite desirable and necessary that a snapacting switch assembly shall be opened and closed at substantially thesame fluid pressure or that the pressure differential be made as smallas possible. A typical example is an oxygen pressure signal switch foruse in an airplane and which is opened to interrupt a warning signalwhen the oxygen has increased to a predetermined value and which must beclosed to establish such warning signal when said oxygen pressure hasdecreased to said predetermined value. Obviously any lag or pressuredifferential in the closing or re-closing of such an oxygen pressureoperated switch could have. dire consequences.

The primary object of the present invention is the provision of a quickacting fluid operated switch assembly which is operated in oppositedirections with a minimum differential between operating pressures.

Another object of this invention is a fluid operated switch assemblyhaving a mechanically stressed diaphragm responsive to an increasing andpredetermined pressure to operate said switch assembly in one directionand including means for causing operation of the switch assembly in theopposite direction when the fluid pressure decreases to substantiallythe same pressure as said predetermined pressure.

A further object of the invention is a fluid operated switch assemblyincluding a snap acting member and one or more means reactingthereagainst so that said switch assembly isoperated in oppositedirections at substantially the same fluid pressure l 2 Still anotherobject is the provision of afluid operated switch assembly of simpleconstruction, easily assembled and thoroughly reliable in operation.

A still further object is the provision of a fluid operated switchassembly including a switch arm actuated by a fluid pressure responsivediaphragm and a pair of loading assemblies, one of which is adjusted todetermine the pressureat which said switch assembly is opened and theother of which is adjusted to cause said switch assembly to close atsubstantially the same pres-- sure.

Other and further objects of the invention will be evident to thoseskilled in the art by the disclosure which follows. Reference is herebymade to the accompanying-drawings wherein similar reference charactersdesignate similar elements and wherein:

Fig. 1 is a longitudinal section through one. form of fluid operatedswitch assembly according Fig. 6 is a perspective detail of the switcharm for the switch assembly of Figs. 1 and 2.

Figs. '7 and 8 are longitudinal cross-sections of the preferred form ofthe fluid operated switchassembly taken respectively on the lines 'l!and --3 of Fig. 12.

9 a cross-section taken on the line 99 of Fig. 7.

Fig. 10 is a perspective detail of the supporting plate for thepreferred form of my fluid operated switch assembly.

Figs. 11 and 12 are crosssections taken respectively on the lines H-Iland l2l2 of Fig. '7.

Fig. 13 is plan view of the inside of the cover member.

Although the illustrated embodiments of my invention are described asresponsive to oxygen or 7 gas pressure it shall be understood that theinvention is also useful for switch assemblies that are responsive toliquid pressure. Hence, the term fluid as used in the specification andclaims means and includes gas and/ or liquid. In addition the inventionin its broadest aspects is not limited to the specific form of switchassem- 3 bly, loading assembly, and/or flexible mechanically stresseddiaphragm shown.

In general both embodiments of the invention comprise a casing providinga chamber for connection to a fluid pressure or fluid supply, a headmember closing said chamber, a flexible diaphragm dividing said chamberinto a pressure compartment and a switch compartment, a switch assemblyin said switch compartment, and means for mechanically loading saiddiaphragm either in the form of a deformed portion in said diaphragmand/or one or two loading assemblies exerting pressure upon saiddiaphragm and particularly upon the deformed portion thereof. In thepreferred embodiment of the invention one of said loading assembliesdirectly engages the free end of the switch arm to flex the same.

The simpler embodiment of the invention shown in Figs. 1-6 inclusive ishoused in a hollow casing I5, having at one end a threaded nipple l6 forconnection to a source of fluid and/or fluid pressure, and having at itsother end a flange IT. A head member 3 is preferably composed of aninsulating material such as Bakelite and has a pair of terminal studs [9and molded therein. Terminal studs l9 and 20 are internally threaded toreceive screws 2! by which electrical connectors may be attached to saidstuds I3 and 29. The inner end of said head member i8 is provided with acircular recess 22 within which is mounted a switch assembly. Suchswitch assembly comprises a contact 23 driven into a hole in the end ofterminal stud 2B and a switch arm 24. Said switch arm 24 has a free end25 carrying a contact 26, has an intermediate enlarged portion 21provided with an opening 28, and has a semi-circular end portion 29 inparallel spaced relation to said portion 21 and provided with a hole 30in alignment with opening 28 but eccentric to said semi-circular portion29. A headed screw 3! extends through hole 33 into the end of the otherterminal stud l9. Said switch arm 24 is arranged for convenient andaccurate mounting because the head of screw 3! is available for drivinthrough opening 28. Also the engagement of the periphery ofsemi-circular portion 29 with the wall of circular recess 22 and theeccentric position of screw 3| accurately maintains said switch arm 24in position with its contact 25 directly opposite contact 23.

A cincular washer 32 of dielectric or insulating material such as papercovers the unrecessed inner end of head member IS. A rigid supportingplate 33 of a metal such as steel is provided with a central hole 34 andhas its edge abutting against said washer 32. A disc 35 is aperturedopposite hole 34 and an insulating cup 36 covers disc 35 and overhangsthe periphery of plate 33, both disc 35 and cup 36 are preferably madeof paper. An actuating pin 3'! has rounded ends and is movably mountedwithin the hole 34 in plate 33.

A flexible diaphragm 38 is mounted adjacent plate 33 and divides theinterior of casing l5 into a switch compartment 39 and a pressurecompartment ill. Said flexible diaphragm 33 is composed of a resilientsheet material such as Phosphor-bronze or copper and according to theinvention is mechanically stressed in such a manner that an area thereofsnaps or moves abruptly from one position to another. The preferredmanner of mechanically stressing said diaphragm 38, particularly whenprovided as a circular disc as shown, is to emboss a circular groove 4|having a semi-circular cross-section concentrically into said diaphragm38. Such embossing of the groove 41 causes diaphragm 38 to assume anover-all concavo-convex form as illustrated by Figs. 4 and 5, that isconcave in the same direction as said groove 4|.

The flexible diaphragm 4| is mounted within casing l5 with itsperipheral faces clamped between cup 36 and a gasket 42 which ispreferably in the form of a ring and composed of a resilient insulatingmaterial such as rubber. Said gasket 42, the diaphragm 38, insulatingcup 36, disc 35, supporting plate 33 and washer 32 are held underpressure or are clamped between a shoulder 43 on the interior of casingl5 and the unrecessed rim of head member 3 by turning or peening overthe flange ll into the position shown in Fig. l and overlying a shoulder44 of head member Ill. Such clamping of the peripheral portions offlexible diaphragm. 38 into a plane causes the central portion thereofto be normally displaced from such plane in the direction away from saidplate 33. The rounded ends of actuating pin 31 respectively centrallyengage the displaced portion of diaphragm 38 and switch arm 24.

An adjustable loading assembly is mounted on head member 18 which ispreferably provided centrally with a bore 45 having a restricted portion45. A flanged bushing 46 is internally threaded and is pressed into thehead member [8 with the flange of said bushing in bore 45 and theremainder of said bushing 43 engaging and extending through therestricted portion 45 of bore 45. A coil spring 41 is placed within bore45, has one end bearing upon the switch arm 24, and has its other endbearing against a fiber disc 43. A small metal disc 49 is adjacent fiberdisc 48 and is engaged by the end of a threaded stem 59 extendingthrough bushing 46. Y

For operation the pressure compartment 40 is connected to a source ofpressure, as by connection of threaded nipple. Hi to a pressurecontainer, and the terminal studs l9 and 20 are electrically connectedto a signal circuit of any known form.

Normally the parts are in the position shown in. Fig. 1 and the signalcircuit is interrupted; An increase in fluid pressure tends to reversethe flexible diaphragm 38 but such tendency is opposed or resisted by.the mechanical stress in diaphragm 38 and by the action of theadjustable loading assembly. However, at a predetermined fluid pressureboth those said resistances are overcome and the diaphragmSB is abruptlyreversed causing rapid movement of pin 31 and rapid closing of theswitch assembly to complete the signal circuit. Since the flexiblediaphragm 38 when reversed abuts against the supporting plate 33 anyfurther increase in pressure can not reverse said diaphragm 38 anyfarther to increase the pressure required to return it to originalposition or to cause damage to said flexible diaphragm 38 if subjectedto an excessive pressure. Consequently, when the fluid pressuredecreases to approximately said predetermined pressure, said diaphragm38 returns to its original position and the switch assembly opensnormally to again interrupt the signal circuit.

By virtue of the mechanical stresses in flexible diaphragm 38 caused bydeformation and/or the co-operative action or reaction of the adjustableloading assembly and/or supporting plate 33. the fluid operated switchassembly just described and shown in Figs. 1 and 2 has a smalldifferential between the fluid pressures at which the switch assembly isclosed and opened. Adjustment of said loading assembly as by turning ofstem 50 either increases or decreases the predetermined fluid pressureat which the switch assembly is operated. For a given design, it hasbeen found that such adjustment to obtain a predetermined operatingpressure has little effect upon the differential between the switchclosing pressure and the switch opening pressure.

The preferred embodiment of the invention is illustrated in Figs. 7-13,inclusive, and in general has'parts corresponding to those of theembodiment shown in Figs. 1-6. The housing 5! for said preferredembodiment comprises an outer cylindrical wall 52 and an inner casing 53provided with a chamber 54. A plurality of irregular ribs 55, see Figs.11 and 12, extend between wall 52 and inner casing 53 and are providedwith a set of four threaded holes 56 located in quadrature and with aset of three threaded holes 57 for purposes to be later explained. A.hollow hexagonal projection53 on the bottom of housing 5! is providedwith a threaded bore 59 for connection to a source of fluid pressure orfluid and a hole 30 extends from the bottom of bore 59 into chamber 54,see Fig. 8.

A ring gasket 6| of a flexible resilient material such as rubber abuts ashoulder 52 within the chamber '54 in casing 53. A flexible diaphragm isprovided with a circular concave groove 64 in the same manner as theflexible diaphragm 33 shown in Figs. 3-5 and is placed adjacent gasket6|. Said diaphragm 63 divides the chamber 54 into a pressure compartment65 and a switch compartment 66.

Asupporting plate 61, preferably made of steel, is provided with acentral hole 68 and an apertured insulating disc 69 and cup 19 areinterposed between supporting plate 6'! and said diaphragm '63. A headmember 1! of insulating material is provided at one end with a circularrecess 12 and has an external intermediate shoulder 13. A soft metalring 14 encircles head member H adjacent shoulder 13. A clamping ring 15is recessed to fit over ring 14 and head member H and a plurality ofmachine screws 15 extend through clamping ring '15 into threaded holes55. Upon tightening of said screws "16 the unrecessed end of head memberH is pressed toward shoulder 62 and ring gasket 5! to clamp the edges ofsupporting plate 51, cup '10, disc 69 and flexiblediaphragm-SBtherebetWeen. As before, such clamping of the peripheralportion of the flexible diaphragm 63 into a plane causes the centralportion thereof to be normally displaced from such plane in thedirection away from said plate 81, see Fig. '7. As a result themechanical stresses in said diaphragm63 resist movement by fluid orfluid pressure until a predetermined pressure is exerted whereupon thediaphragm 53 and particularly the central portion thereof within groove54 are abruptly reversed, see Fig. 8. The supporting plate 8'! and/orthe disc 69 limit such reversing movement of said diaphragm 63 tocontribute to the minimizing of the differential pressure betweendiaphragm operation.

The head member H has a hollow connector stud l! embedded or mouldedtherein and is provided with a pair of polygonal holes 78 and 19 eachrespectively having restricted circular portions 18' and '19 adjacentthe outer face of head member 1| Said head member H is alsoprovided witha lateral recess 8H and a hole'ill extending from said recess 80 intothe circular recess 12. Preferably the polygonal or hexagonal .hole 18extends through the center of head member Hand the stud 1.1 and holesI9, and 8.! are arranged at angular spacings of 90, see Fig. 9, althoughother arrangements of the stud and holes maybe employed.

The switch elementsinclude a switch arm :82, having a free end carryinga contact 83 for en gaging a contact 84 riveted to the supporting plate61. Said switch .arm 82 has a rerenforcing strip 82' and has its fixedend curved to correspond to the curvature of theadjacent wall of thecircular recess 1 2. A cross strip 85 overlays the curved end of switcharm 82 anda self-threading screw 85 extends therethrough and into oneend of the hollow connector stud 1.1. The screw .86 is off-centerwith'respect to the curved fixed end of said switch, arm 82 which isconsequently readil and securely mounted with contacts 33 and 84 injuxtaposition. A hollow connector post 8'! is fastened to supportingplate 87 and is .located to extend through the hole-8.! and into thelateral recess t'ifl in head member 1 l. The-switch arm '82 is providedwith a lateral notch 88 for clearance of said vpost '81, see Fig. 9. Thesup,- porting plate "5'! is preferably of iron or steel to provide thenecessary rigidity and wouldhordinarily ofier considerable resistance toelectrical currents flowing from contact 84 to post 81. Consequently,the supporting plate 6.], contact .8 and post8'l arecoated with a metalof high electrical conductivity and are preferably electrolyticallsilver plated.

An actuating pin 89 is movably mounted within the hole 58 in plate 51,is preferably composed of aninsulating material and has rounded endsrespectively engaging the-central portion of flexie ble diaphragm 63 andswitch arm 82. Since the switch assembly is intended to complete asignal circuit for all fluid pressures below a predetermined pressure,the switch arm .32 is normally closed when diaphragm'iiS is in the;position shown in Fig. 7. Reversal of diaphragm 63 throughthe medium ofactuating pin .89 moves said switch arm 82. to open contacts 83 and 84.'However, there may be some differencebetween the switch openingpressure and switch closing Dressurc which. createsa dangerous conditionwhen .the fluid operated switch assembly is employed as. a signal switchfor'lowv pressure in the. oxygen sup, ply of'an airplane. Thereforaanimportant'feature of'the invention istheprovision of apair .ofadjustable loading assemblies whereby the ,predetermined pressure forswitch operationfmay be varied and the switch initiating and returnpressures are substantially equal.

Such adjustable loading assemblies may be similar in construction,one'being located for a point .of application on said switch arm,82 di-vrectly opposite actuating pin 89 and the other beinglocated to act uponthe 'freeend of said switch arm 32 and preferably opposite a fixedabutment which may be in the form of a Contact 84 on supportingplateB'l. Said one loading assembly includes an internally threadedbushing 90having at one enda'hexagonal head within polygonal hole18 andengaging the walls thereof and spun over at the other end to engage theouterface of head member H. A coil spring 9| Within holei18 has one endencircling the stem of a pin 92 in contact with switch. arm.82opposite'actuating pin .'89 and has its other end bearing against aninsulating disc'93. An adjusting screw'94 is threaded into bushing 90,.has its inner end abutting a metal disc 95 adjacent insulating disc'93,and is secured in adjusted no sition'by a lock nut The other loadingassembly includes an internally threaded bushing 91 having at one end ahexagonal head within polygonal hole 19 to engage the walls thereof andspun over at the other end to engage the outer face of head member II. Acoil spring 98 within hole 19 has one end encircling the stem of a pin99 in contact with the free end of switch arm 82 opposite contacts 83and 84 and has its other end bearing against an insulating disc I00. Anadjusting screw IN is threaded into bushing 91, has its inner endabutting a metal disc I02 and is secured in adjusted position by a locknut I03.

The fluid operated switch assembly is preferably sealed to preventinfiltration of dust and dirt and/or accidental or other movement of theadjusting screws 94 and IN. For this purpose a cover I 23 has a rabbetedrim I04 fittin into cylindrical wall 52 of housing 5| and machine screwsI05 extend through holes I06 in said cover I23 and into engagement withthe threaded holes 51 in ribs 55. A pair of bolts I01 extend from thebottom of housing 5I and receive nuts I08 whereby the switch assemblymay be mounted on a panel or in any other desired position.

The electrical connections may conveniently be made through cover I23and so as to be interrupted upon removal thereof. To this end aconductor strip I09 has one end fastened to an insulating plate IIO bythe riveted end of a split plug III having a collar III and a conductorstrip II2 has one end fastened to said insulating plate I I by theriveted end of a, split plug II3 having a collar H3. Said insulatingplate H0 and an interposed insulating layer II4 are fastened, as byrivets II5, to the inside of cover I23 and in such position that plugIII enters and engages the interior of hollow connector stud TI and plugH3 enters and engages the interior of hollow connector post 81 whencover I23 is placed upon the housing 5|. A hollow socket II6 extendsfrom cover I23 and a pair of connector prongs I I! are within saidsocket II6, ex-

housing 5| will, when a predetermined pressure is reached, causeflexible diaphragm 63 abruptly to reverse and move activating pin 89 andswitch arm 82 so that contacts 83 and 84 are opened. Also when saidfluid pressure is decreased the diaphragm 63 abruptly returns to itsoriginal position and contacts 83 and 84 are closed. Hence a signalcircuit containing the switch assembly is effected only when the fluidpressure is above said predetermined pressure.

It has been found that adjustment of the two loading assemblies can beaccomplished so that there is very little, if any, difference betweenthe switch initiating pressure and the switch return pressure. Forinstance adjustment of screw 94 to increase the pressure exerted byspring 9| and pin 92 against the switch arm 82 also increases theloading on flexible diaphragm 63 through actuating pin 89 so that ahigher fluid pressure is required to operate said diaphragm and opencontacts 83 and 84. Conversely adjustment of screw 94 in the oppositedirection will decrease the fluid pressure necessary to operatediaphragm 63 and open contacts 83 and 84. However, the mechanicalstresses set up in flexible diaphragm 63 upon reversal thereof and whichmust be overcome for return to original position opposesuch return andordinarily make it necessary for the fluid pressure to decrease somewhatbelow that at which the assembly first operated and before the samereturns to its original position.

Adjustment of screw IOI to increase the pres-- sure exerted by spring 98and pin 99 against the free end of switch arm 82 will increase the fluidpressure at which said diaphragm 63 returns to its original position andsuch return pressure can be adjusted to approach and substantially equalthe switch. initiating pressure. Inasmuch as the point of applicationfor the loading assembly controlling the switch return pressure isopposite the fixed contact 84 on the rigid supporting plate 61, theaction of such loading assembly generally has no appreciable effect uponthe switch initiating pressure because most of loading is applied to thefixed contact 84 and little. if any, is transmitted through the switcharm 82 and actuating pin 89 to the flexible diaphragm 63. However, uponthe opening of switch arm 82 and contacts 83 and 04, the loading of suchassembly is no longer received by fixed contact 94 but is transmitted tosaid actuating pin 89 and the thin reversed flexible diaphragm 63immediately to oppose, together with loading assembly controlling theswitch initiating pressure, the mechanical stresses in the reversedflexible diaphragm (53 and to approach very nearly the equilibriumcondition for return of the flexible diaphragm 63 to its originalposition. As a result, when the fluid pressure decreases to or onlyslightly beyond the switch initiating pressure, the mechanical stressesin the reversed flexible diaphragm 63 are overcome and the switchassembly returns to its original or closed position.

Although not necessary, it is preferable first to adjust the switchinitiating pressure and then to adjust the switch return pressure. Alsoduring calibration it is advisable to check and adjust the switchinitiating pressure and switch return pressure more than once.

Within the limits of any particular design it is possible by employmentof the present invention to minimize the differential between switchinitiating and return pressures over a considerable range of pressures.

Those skilled in the art will recognize that the opened and closedpositions of the switch assemblies shown may be reversed as required andthat reversal of switch operation in the preferred em bodiment merelyrequires the substitution of a non-conducting abutment in place ofcontact 84 and opposite the point of application of the loading assemblyfor controlling the switch return pressure. The present disclosure ismerely illustrative and other variations of the fluid operated switchassembly are Within the scope of the invention as defined in the claimswhich follow.

Having now particularly described my invention, what I desire to secureby Letters Patent of the United States and what I claim is:

1. A fluid operated switch assembly comprising a casing providing achamber for connection to a source of variable fluid pressure, a headmember closing said chamber, a flexible diaphragm dividing said chamberinto a pressure compartment and a switch compartment, said diaphragmbeing mechanically stressed toward said pressure compartment, a switchassembly within said switch compartment and having a switch arm movableto closed, and open positions and operatively connected to saiddiaphragm for movement to open position upon reversal of said diaphragm,and a loading assembly engaging and urging said switch arm to closedposition and exerting a loading pressure on said diaphragm when the sameis reversed to minimize the differential between the fluid pressures forreversal and return of said diaphragm and for opening and closing ofswitch assembly.

2. A fluid operated switch assembly comprising a casing providing achamber for connection to a source of variable fluid pressure, a headmember for closing said chamber, a flexible diaphragm dividing saidchamber into a switch compartment and pressure compartment, an annularcorrugation in said diaphragm mechanically stressing the central portionof the same away from said switch compartment and adapted to be abruptlyreversed by a predetermined fluid pressure, a switch assembly withinsaid switch compartment having a switch arm adapted to be opened andclosed by reversal of said central portion of the diaphragm, and aloading assembly engaging and urging said switch arm to closed positionand exerting a pressure on the central portion of said diaphragm whenthe same is reversed to minimize the differential between the fluidpressures for reversal and return of said diaphragm and for opening andclosing of said switch assembly.

3. A fluid operated switch assembly comprising a casing providing achamber for connection to a source of variable fluid pressure, a headmember for closing said chamber, a flexible diaphragm dividing saidchamber into a switch compartment ing a casing providing a chamber forconnection to a source of fluid pressure, a head member. for closingsaid chamber, a flexible diaphragm dividing said chamber into a switchcompartment and; a pressure compartment, said diaphragm having adeformed portion mechanically stressing the same toward said pressurecompartment and adapted to be reversed abruptly by a predetermined fluidpressure, a supporting plate in said switch compartment adjacent saidflexible diaphragm to limit reversal thereof, a switch assembly withinsaid switch compartment and including a switch arm adapted to be openedand closed by reversal of said diaphragm and including a contact on saidplate and engaged by said switch arm in its closed position, and aloading assembly mounted in said head member and engaging said switcharm at a point opposite said contact and for exerting a restoring forceon said diaphragm when said switch arm is in open position.

6. A fluid operated switch assembly comprising a casing providing achamber for connection to a source of fluid pressure, a head member forclosing said chamber and provided with a circular recess, a switchassembly including a switch arm having an elongated contact arm at oneend, a semi-circular portion at the other end, and an enlargedintermediate portion provided with an opening, and bent to bring saidsemi-circular end portion and enlarged intermediate portion into spaced.relation, and a fastening means attaching said switch arm to said headmember with V the periphery of said semi-circular end portion and apressure compartment, a supporting plate in said switch compartmentadjacent said flex-- ible diaphragm, a deformed portion in saiddiaphragm, mechanically stressing the same away from said plate, andadapted to be abruptly reversed and pressed against said plate by apredetermined fluid pressure, a switch assembly within said switchcompartment and including a switch arm adapted to be opened by reversalof said diaphragm, and a loading assembly urging said switch arm toclosed position and exerting a force on said flexible diaphragmprimarily when said diaphragm is reversed and for returning saiddiaphragm to normal position at substantially said predetermined fluidpressure.

4. A fluid operated switch assembly comprising a casing providing achamber for connection to a source of variable fluid pressure, a headmember for closing said chamber, a flexible diaphragm dividing saidchamber into a switch compartment and a pressure compartment, asupporting plate in said switch compartment adjacent said flexiblediaphragm which is deformed and normally stressed toward said pressurecorn- Dartment and away from said supporting plate, a switch assemblywithin said switch compartment and including a switch arm adapted to beopened by reversal of said diaphragm and including an abutment on saidsupporting plate and engaging said switch arm when said diaphragm is innormal position and said switch arm is closed, and a loading assemblyengaging said switch arm opposite said abutment and for exerting arestoring force on said diaphragm when it has moved said switch arm awayfrom said abutment.

5. A fluid operated switch assembly comprisengaging the wall of saidcircular recess and having a head opposite to and accessible through theopening in said enlarged intermediate portion.

7. A fluid operated switch assembly comprising a casing providing achamber for connection to a source of fluid pressure, a head member forclosing said chamber, a flexible diaphragm dividing said chamber into aswitch compartment and a pressure compartment and mechanically stressedin one direction and adapted to be abruptly reversed by a predeterminedfluid pressure, a switch assembly within said switch compartment andhaving a switch arm moved by re-, versal of said diaphragm from oneposition to another position, and a pair of loading assemblies arrangedto exert their loads upon said flexible diaphragm in opposition to saidfluid pressure, one of said assemblies exerting its load upon saiddiaphragm at all times to determine a diaphragm initiating fluidpressure and the other of said assemblies exerting its load upon saiddiaphragm only when the same is reversed and for rendering the diaphragmreturn pressure substantially equal to said diaphragm initiatingpressure.

8. A fluid operated switch assembly comprising a casing providing achamber for connection to a source of fluid pressure, a head member forclosing said chamber, a flexible diaphragm dividing said chamber into aswitch compartment and a pressure compartment and mechanically stressedin one direction and adapted to be abruptly reversed by a predeterminedfluid pressure, a switch assembly within said switch compartment andincluding a switch arm adapted to be opened and closed by reversal ofsaid diaphragm, and a pair of loading assemblies each having a memberengaging said switch arm at displaced points of application, one of saidassemblies exerting a load to determine the switch initiating pressureand the other of said as- 1 l semblies exerting a load upon said switcharm such that the switch return fluid pressure is substantially the sameas said switch initiating fluid pressure.

9. A fluid operated switch assembly comprising a casing providing achamber for connection to a source of fluid pressure, a head member forclosing said chamber, a flexible diaphragm dividing said chamber into aswitch compartment and a pressure compartment and mechanically stressedin one direction and adapted to {be abruptly reversed by a predeterminedfluid pressure, a switch assembly within said switch compartment andhaving a switch arm moved by reversal of said diaphragm from oneposition to another position, an abutment in said switch compartment andlocated to engage said switch arm in said one position thereof, and apair of loading assemblies each having a member engaging said switch armat displaced points of application one of which is opposite saidabutment whereby the load of such assembly is transmitted to saidabutment when said switch arm is in said one position and is applied tosaid switch arm and flexible diaphragm when said switch arm is in saidother position and said diaphragm is reversed.

10. A fluid operated switch assembly compris ing a casing providing achamber for connection to a source of fluid pressure, a head member forclosing said chamber, a flexible diaphragm dividing said chamber into aswitch compartment and a pressure compartment and mechanically stressedin one direction and adapted to be abruptly reversed by a predeterminedfluid pressure, a supporting plate in said switch compartment adjacentsaid flexible diaphragm to limit reversal thereof, a switch assemblywithin said switch compartment, including a contact on said plate and aswitch arm having a free end movable into and out of engagement withsaid contact, an actuating member movably mounted between said diaphragmand said switch arm and for transmitting the movement of said flexiblediaphragm to said switch arm, and a pair of loading assemblies mountedin said head member and each having a member engaging said switch atdisplaced points of application, one of said members engaging saidswitch arm opposite the contact on said plate and the other of saidmembers engaging said switch arm opposite said actuating member.

11. A fluid opera-ted switch assembly comprising a casing providing achamber for connection to a source of fluid pressure, a head member forclosing said chamber, a flexible diaphragm dividing said chamber into aswitch compartment and a pressure compartment, a stationary supportingplate in said switch compartment adjacent said flexible diaphragm tolimit movement thereof by fluid pressure, and a switch assembly withinsaid switch compartment and including a contact on said supportingplate, said contact and said supporting plate constituting an electricalpath to said switch assembly.

12. A fluid opera-ted switch assembly compris ing a casing providing achamber for connection to a source of fluid pressure, a head member forclosing said chamber, a flexible diaphragm dividing said chamber into aswitch compartment and a pressure compartment, a stationary supportingplate in said switch compartment adjacent said flexible diaphragm tolimit movement there-- of by fluid pressure, a switch assembly withinsaid switch compartment and including a contact on said supportingplate, and a connector mounted on said plate and extending through saidhead member.

13. A fluid operated switch assembly com-prising a casing providing achamber for connection to a source of fluid pressure, a head member forclosing said chamber, a flexible diaphragm dividing said chamber into aswitch compartment and a pressure compartment, a stationary supportingplate in said switch compartment adjacent said flexible diaphragm tolimit movement thereof by fluid pressure, a switch assembly within saidswitch compartment and including a contact on said supporting plate, aconnector stem mounted on said plate and extending through said headmember, and a coating of high electrical con-' ductivity covering saidplate, contact and stem.

14. A fluid operated switch assembly comprising a casing providing achamber for connection to a source of fluid pressure, a head member forclosing said chamber, a flexible diaphragm dividing said chamber into aswitch compartment and a pressure compartment, a stationary supportingplate in said switch compartment adjacent said flexible'diaphragmtolimit movement there-- of by fluid pressure, a switch assembly withinsaid switch compartment and including a contact on said supporting plateand a switch arm provided with an opening, and a connector stem mountedon said plate and extending through said opening in said switch arm andthrough said head member.

15. A fluid operated switch assembly comprising a casing providing achamber for connection to a source of fluid pressure, an insulating headmember for closing said chamber, provided with three holes indiametrically spaced relation, and having a connector sleeve in one ofsaid holes, a switch arm having one end fastened to said sleeve andextending over said other two holes, and a pair of adjustable loadingassemblies each mounted in one of said other two holes and eachcomprising an internally threaded sleeve attached to said head member, aspring member within said hole and having one end exerting a pressureupon said switch arm, and a threaded stem extending through said sleeveand engaging the other end of said spring member.

16. A fluid operated switch assembly comprising a casing providing achamber for connection to a source of fluid pressure, an insulating headmember for closing said chamber, and provided with a polygonal holehaving a restricted portion at the outer end thereof, and a bushinghaving at its inner end a polygonal head complementary to said hole,having 13, central portion in the restricted portion of said hole, andhaving at its outer end a deformed flange engaging said head member.

17. A fluid operated switch assembly com-prising a casing providing achamber for connection to a source or fluid pressure, a head member forclosing said chamber and provided with a central hole and three holesspaced in quadrature therearound, a hollow connector sleeve in one ofsaid three holes, a flexible diaphragm dividing said chamber into aswitch compartment and a pressure compartment, having a deformed portionmechanically stressed toward said pressure compartment and adapted to bereversed abruptly by fluid pressure, a supporting plate in said switchcompartment adjacent said flexible diaphragm to limit its movement bysaid fluid pressure and provided centrally with an opening, a switchassembly within said switch compartment and in- 13 eluding a contact onsaid supporting plate and a switch arm fastened to said connectorsleeve, overlying said central hole and the diametrically opposite hole,and provided with a lateral notch, a hollow connector stem mounted onsaid plate and extending through said notch and said head member, anactuating member movably mounted within the opening in said plate andengaging said switch arm and the deformed portion of said flexiblediaphragm, a pair of adjustable loading assemblies in said head member,one in the central hole opposite said actuating member and the other inthe hole opposite the contact on said plate, and a cover member for saidcasing and carrying a pair of spaced connector terminals adapteddetachably to engage respectively said hollow connector sleeve and saidhollow connector stem when said cover member is fitted onto said casing.

FRANK ROBERT BEAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

